1. Field
The present invention relates to disk drives for computer systems. In particular, the present invention relates to a disk drive comprising a double sided flex circuit wherein a first side lead provides an etching mask for a second side lead.
2. Description of the Related Art
FIG. 1A shows a prior art disk drive comprising a disk 2 and a head 4 connected to a distal end of an actuator arm 6 which is rotated about a pivot by a voice coil motor (VCM) 8 to position the head 4 radially over the disk 2. The head 4 may comprise an inductive write element (write coil) and a magnetoresistive read element (MR element) fabricated in very small dimensions using semiconductor fabrication techniques. A flex circuit 10 is typically employed to electrically couple the head 4 to control circuitry within the disk drive. In the example shown in FIG. 1A, a first flex circuit 10A couples the head 4 to a preamp 12A mounted on the actuator arm 6, and a second flex circuit 10B couples the preamp 12A to other control circuitry 12B mounted on a printed circuit board, wherein the second flex circuit 10B facilitates the movement of the actuator arm 6. In other disk drives, the preamp 12A may be integrated with control circuitry 12B such that flex circuit 10A couples the head 4 directly to the control circuitry 12B mounted on the printed circuit board.
FIG. 1B shows a magnified cross-sectional view of the flex circuit 10A as comprising electrical leads for carrying differential signals, such as a differential write signal 14A and 14B and a differential read signal 16A and 16B for the head 4. The electrical leads are supported by a substrate 18 which may comprise any suitable material, such as a polyimide. The electrical leads are typically formed using conventional etching techniques on one side of the substrate 18 such that the electrical leads for carrying the differential signal are separated by an air gap (e.g., air gap 20A and 20B).
As the data rate in disk drives increases into the microwave region, the transmission properties of the electrical leads for carrying the differential signals has become more significant. For example, it is desirable to reduce the impedance of the electrical leads in order to increase power efficiency as well as the signal-to-noise ratio (SNR) of the differential signal.
There is, therefore, a need in a disk drive to reduce the impedance of the electrical leads fabricated on a flex circuit in order to improve the power efficiency and SNR in transmitting differential signals along the electrical leads.